An intervertebral disc may be subject to degeneration due to trauma, disease, and/or aging. Treatment of a degenerated disc may include partial or full removal of the intervertebral disc. This may destabilize the spinal column resulting in subsidence or deformation of vertebrae and possible alteration of the natural separation distance between adjacent vertebrae. During spinal fixation surgery, a spinal implant can be inserted in the space created by the removal or partial removal of the intervertebral disc between adjacent vertebrae. The spinal implant may maintain the height of the spine and restore stability to the spine. Maintaining the appropriate distance between the vertebrae helps reduce the pressure applied to nerves that pass between the vertebral bodies, thereby reducing pain and nerve damage.
Various types of spinal implants may be inserted into the space provided by the discectomy. The spinal implant may be a fusion device that allows bone growth to fuse the implant to the adjacent vertebrae. One type of implant used to promote fusion includes a pair of engaging plates and struts. The engaging plates engage the vertebrae and the struts separate the engaging plates to provide the appropriate separation. The engaging plates can be selected to achieve a desired lordotic angle. Implants having engaging plates and struts are described in U.S. Pat. No. 6,045,579 by Hochschuer et al., U.S. Provisional Patent Application No. 60/363,219 by Landry et al. and U.S. patent application Ser. No. 10/387,361 by Landry et al., each of which is fully incorporated by reference herein.
Spinal implants as described above can provide the proper lordotic alignment and vertebral separation for a particular patient. Such implants, however, typically rely on the compressive forces of the spine to hold them in place. The spinal implant, however, may move laterally causing the implant to become misaligned.